In a process in which a mobile terminal such as a User Equipment (UE) communicates with a network, no matter what type of service is initiated, a random access process needs to be initiated first, so that an Radio Resource Control (RRC) connection is established between the UE and an Radio Network Controller (RNC), thereby implementing data exchange between the UE and the network. The random access process specifically refers to that the UE obtains an access probability according to an Access Service Class (ASC), and randomly selects one or more available access timeslots from available access timeslots of a current cell of the UE according to the obtained access probability to send an access preamble to a base station (Node B) until the UE receives an acquisition indication from the base station.
The higher the access probability obtained through a calculation is, the more the randomly selected available access timeslots for sending the access preamble of the UE are, and therefore, the higher a possibility of service access success is. In addition, the ASC is used to indicate a priority of a service currently initiated by the UE. Generally, according to an importance or emergency level of a service, the ASC is classified into eight classes, which are specifically represented by eight digits 0 to 7. ASC=0 represents a highest priority, and a typical service is an emergency call; ASC=7 represents a lowest priority. In the prior art, when a service is an access service with the highest priority, such as an emergency call, that is, ASC=0, the obtained access probability is a fixed value 1. That is to say, regardless of a state of a current network or that of the UE, an access probability of a service whose ASC is 0 is always 100%.
However, due to a limited network capacity, access requirements of services with the highest priority, such as emergency calls, increase significantly when a special event, for example, a large-scale disaster event, occurs. This results in network congestion. In addition, because an access probability of each access service is 100%, an upper limit of the network capacity is exceeded. As a result, all access services with the highest priority are likely to fail simultaneously, and a communication network system is unavailable.